1. Field of the Invention
Relates to railroad-highway transport apparatus generally and particularily to trailer handling, TOFC -- trailer-on-flatcar transportation. This invention is an improvement on my earlier inventions, U.S. Pat. No. 3,610,169 titled Road-Rail Transport Apparatus, and U.S. Pat. No. 3,370,551 titled Railroad-Highway Transport Apparatus and Method.
2. Description of the Prior Art
In present practice, the typical TOFC car is adapted for use in transporting two highway semitrailers and is provided with a forward and a rearward trailer hitch for engaging the kingpin of the trailers. The trailer loading/unloading procedure and use of the trailer hitches may be considered to be car-side loading and car-end loading: car-side loading is generally done in high-volume TOFC terminals equipped with a mobile crane or heavy duty lift truck, and the trailers are bodily lifted and manipulated in loading and unloading the cars.
In the car-end loading/unloading procedure, a string of cars is backed against a ramp with all the cars facing the same direction, the car-mounted bridge plates are folded down between the cars, and the trailers, each in succession are maneuvered by a tractor onto or off the cars. The trailer hitches are raised for anchoring the kingpins of the trailers or retracted for permitting passage of the trailers and tractor on the string of cars.
There are many problems attendant existing trailer-handling practices: In the typical TOFC terminal, using car-side loading/unloading procedure, the operation of the mobile crane or lift truck equipment is paramount. In certain TOFC terminal locations, a single lift truck or crane may handle each trailer. The cost of such heavy-lifting equipment is high, it is generally captive equipment, its design and function is limited, and when it breaks down or malfunctions, a TOFC operation is greatly hampered.
In the existing car-end loading/unloading procedure, marshalling or turning the cars so that they face the same direction is costly in time, labor and equipment use. Considerable skill on the part of a tractor driver is needed for backing a loaded tractor-trailer rig up a ramp and along the elevated decks and bridges of a string of cars. At the loading of each trailer on a car, the trailer hitch is retracted, the trailer is backed over the hitch, and the hitch is then raised and latched to the kingpin. This procedure is carried out for each trailer and each car successively -- a rather slow, arduous operation.
The manipulation and proper latching of the trailer hitches requires considerable practice and effort. Many hitches are raised and retracted by use of an electric-powered rotary tool. Such tools are rather awkward and inconvenient to use and require an electric current supply line. It is not unusual for a hitch to become inoperative or malfunction to the extent that it cannot be used. In such instances, a car may carry only a half load or only one trailer, resulting in wasted cargo space and inefficiency.
There is the tendency of the trailers to rock laterally, sometimes violently, while they are being transported on a car. This places heavy strain forces on the trailer hitch and kingpin area of a trailer and can shift or damage the trailer cargo. A trailer manufactured for TOFC service generally is provided with extra strong or reinforced construction at the kingpin area, resulting in increased cost and weight of the trailer.